Magnetism behaviours dominated by the interplay of magnetic anisotropy and exchange coupling in local CoII7 discs

Disc-like CoII7 core-derived (4,4)- and (3,6)-connected layers, {[Co7(C2H5OH)1.5(H2O)0.5(Hdatrz)2(μ3-OH)4(ip)5]·2.5H2O·C2H5OH}n (1) and [Co7(H2O)4(ade)2(μ3-OH)6(sip)2]n (2) (Hdatrz = 3,5-diamino-1,2,4-triazole, ade− = adeninate, ip2− = isophthalate and sip3− = 5-sulfoisophthalate) were solvothermally generated and structurally and magnetically characterized. The effect of magnetic anisotropy and exchange coupling from the local CoII7 cores on the resulting magnetism properties are discussed. A crystallographically asymmetric CoII7 core in 1 exhibited an unusual single-molecule magnet (SMM)-like response under zero dc field resulting from strong anisotropy generated by two different types of CoII polyhedra and highly anisotropic exchange interactions. By contrast, a highly symmetric CoII7 disc in 2 belonging to the C2h point group showed only strong ferromagnetic exchange, to lead to an overall ST = 7/2 spin ground-state at low temperature. Thus, the interplay of magnetic anisotropy and exchange coupling has a great and complicated influence on the overall magnetic phenomena, which should be fully considered for the design and preparation of new CoII-SMMs.